Washing machine and method for controlling the same

ABSTRACT

Method for controlling a washing machine having a drum of which rotation speed is adjustable, including a first step for rotating the drum at a first rotation speed set at control unit, a second step for detecting whether resonance occurs or not at the drum rotating at the first rotation speed, and a third step for changing the rotation speed of the drum if the resonance is detected at the drum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application Nos.P2004-013268, and P2004-013269, both filed on Feb. 27, 2004, which arehereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to washing machines, and moreparticularly, to method and device for preventing resonance fromoccurring in spinning of a washing machine.

2. Discussion of the Related Art

In general, the washing machine washes laundry by softening action ofdetergent, and friction of the laundry with water circulation caused byrotation of a pulsator or drum. Recently, demands for drum type washingmachines increases day by day, which can reduce an entire heightcompared to a pulsator type washing machine, and prevent wrinkles fromforming.

FIG. 1 illustrates a section of a related art drum type washing machine.

Referring to FIG. 1, the related art drum type washing machine isprovided with a tub 3 inside of a cabinet 5 which forms an outerappearance of the drum type washing machine, and a drum 9 rotatablymounted on an inside of the tub 3. The cabinet 5 has a door 1 on a frontfor introduction of laundry, with a gasket 2 between the door 1 and thetub 3.

The tub 3 has springs 4 each with one end secured to an upper outsidecircumference thereof and the other end secured to the cabinet 5, and afriction damper 10 thereunder for damping vibration.

On a rear of the tub 3, there is a motor 6 directly coupled to the drum9 with a rotation shaft 13. On front and rear portion of the rotationshaft 13, there are bearings 12 provided thereto, and on a rear surfaceof the tub 3, there is a bearing housing for supporting the bearing 12.

The motor 6 is provided with a stator 7 and a rotor 8, wherein thestator 7 is mounted to the rear surface of the tub 3, and the rotor 8 isfixed to the rotation shaft 13. Therefore, when the rotor 8 rotates, thedrum 9 connected to the rotor 8 rotates at the same time.

There is a sensor (not shown) at one side of the motor 6 for detecting arotation speed of the rotor 8, and on an upper portion of a frontsurface of the cabinet 5, there is a control panel having variousbuttons for controlling operation of the washing machine.

In the meantime, upon introduction of the laundry into the drum 9, andselecting a washing course, a washing cycle and a rinsing cycle areperformed, and a spinning cycle is performed after above cycles arefinished.

In the spinning cycle of the laundry, the rotation speed of the motor 6is increased gradually until the rotation speed reaches to a presetspeed when the preset speed is maintained for a preset time period. Inthis instance, even though a water extraction performance isproportional to the rotation speed of the motor 6, the rotation speedmay vary with an extent of eccentricity of the laundry. That is, if theeccentricity of the laundry is great, the rotation speed of the drum 9drops, or the rotation shaft 13 suffers from damage. Therefore, it isrequired to measure the eccentricity before the spinning of the washingmachine starts.

In the meantime, during the spinning, there can be resonance occurred atthe washing machine installed on a floor at a particular rotation speedof the motor 6. That is, if the rotation speed of the motor and the drumapproaches close to a natural frequency of the frame, such as thecabinet and the like, the resonance occurs, and once the resonanceoccurs, vibration and noise become very heavy.

The heavy vibration and noise gives a feeling of inconveniencesignificantly in measuring the eccentricity of the laundry or inspinning the laundry, or damages the laundry. Moreover, the heavyvibration and noise drops reliability of user on the product.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a washing machine, anda method for controlling the same that substantially obviates one ormore problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a washing machine forpreventing resonance from occurring during spinning of the washingmachine, and a method for controlling the same.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod for controlling a washing machine having a drum of which rotationspeed is adjustable includes a first step for rotating the drum at afirst rotation speed set at control unit, a second step for detectingwhether resonance occurs or not at the drum rotating at the firstrotation speed, and a third step for changing the rotation speed of thedrum if the resonance is detected at the drum.

The third step includes the step of storing the changed rotation speedin the control unit. The drum is rotated at the changed rotation speedwhen the washing machine is put into operation again after the washingmachine is stopped.

The third step further includes the step of measuring eccentricity oflaundry held in the drum rotating at the changed rotation speed. Thestep of decreasing the rotation speed of the drum again after increasingthe rotation speed of the drum is repeated, if the eccentricity isgreater than a preset value.

The drum may be rotated in regular/reverse directions alternately for aplurality of times, if the eccentricity exceeds a preset value.

In a case the eccentricity is below the preset value, the third stepfurther includes the steps of rotating the drum at the set secondrotation speed for extracting water from the laundry, detecting whetherthe resonance occurs at the drum rotating at the second rotation speedor not, changing the rotation speed of the drum, if the resonance isdetected at the drum, and storing the changed rotation speed in thecontrol unit.

The method further includes the step of measuring the eccentricity ofthe laundry held in the drum, if no resonance occurs in the second step.The step of decreasing the rotation speed of the drum again afterincreasing the rotation speed of the drum is repeated, if theeccentricity is greater than a preset value. The drum is rotated inregular/reverse directions alternately for a plurality of times, if theeccentricity exceeds a preset value.

In a case the eccentricity is below the preset value, further includesthe steps of rotating the drum at the set second rotation speed forextracting water from the laundry, detecting whether the resonanceoccurs at the drum rotating at the second rotation speed or not,changing the rotation speed of the drum, if the resonance is detected atthe drum, and storing the changed rotation speed in the control unit.

The rotation speed of the drum increases in the third step. The rotationspeed of the drum decreases in the third step. The rotation speed of thedrum changes by predetermined magnitudes each greater than 50 rpm in thethird step.

The resonance of the drum is detected by a resonance detecting deviceautomatically in the second step. The third step is performedautomatically by the control unit which receives a signal from theresonance detecting device.

The second step includes the step of sounding alarm through a speaker ifthe resonance of the drum is detected. The steps are performed in astate a test mode is selected.

In another aspect of the present invention, a method for controlling awashing machine having a drum of which rotation speed is adjustable forextracting water from laundry, includes a first step for rotating thedrum at a second rotation speed set at a control unit, a second step forincreasing the rotation speed from the second rotation speed bypredetermined magnitudes of rpm in succession, and whether resonanceoccurs or not at every rotation speed section is detected, a third stepfor changing the rotation speed of the drum when resonance of the drumis detected, and a fourth step for storing the changed rotation speed inthe control unit.

The first step includes the steps of selecting one of course relevant toa kind of laundry, and rotating the drum at the second rotation speedfor the selected course.

The rotation speed of the drum increases in the third step. The rotationspeed of the drum may decrease in the third step. The rotation speed ofthe drum changes by predetermined magnitudes each greater than 50 rpm inthe third step.

The steps are performed in a state a test mode is selected. The drum isrotated at the changed rotation speed when the washing machine is putinto operation again after the test mode is finished.

Not the changed rotation speed, but the second rotation speed isdisplayed on a display, when the washing machine is put into operationagain after the washing machine is stopped. The fourth step includes thestep of sounding an alarm from a speaker when the changed rotation speedis stored.

The third step is performed automatically by the control unit having thesignal received from a resonance detecting device. The second stepincludes the step of automatic detection of resonance occurrence at thedrum by the resonance detecting device.

The second step further includes the step of storing a preset maximumrotation speed in the control unit in a case no resonance occurs untilthe drum rotates up to the preset maximum speed. The second step furtherincludes the step of sounding an alarm from a speaker if the resonanceof the drum is detected.

In the meantime, in another aspect of the present invention, a washingmachine includes a motor for generating rotating force, a drum for beingrotated upon receiving driving force from the motor, a sensor forsensing rotation speed of the drum, a vibration detecting device fortransmitting a signal if vibration greater than a preset value isdetected at the drum, and a control unit for adjusting the rotationspeed of the motor to prevent the resonance of the drum from occurringupon reception of the signal.

The washing machine further includes a rotary key electrically connectedto the control unit for a user to turn to change the rotation speed ofthe drum. The washing machine further includes a selection buttonconnected to the control unit for selecting a course for a kind oflaundry. The washing machine further includes a storage button connectedto the control unit for storing an adjusted rotation speed.

The washing machine further includes a test mode button connected to thecontrol unit for performing a test mode to search a rotation speed atwhich the resonance of the drum occurs. The washing machine furtherincludes a speaker connected to the control unit for sounding an alarmwhen a working rotation speed is stored. The washing machine furtherincludes a display for displaying a rotation speed of the drum sensed atthe sensor.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings;

FIG. 1 illustrates a section of a related art drum type washing machine;

FIG. 2A illustrates a frontal perspective view of a washing machine;

FIG. 2B illustrates a graph showing variation of rotation speed duringprogress of spinning of a washing machine;

FIGS. 3A˜3C illustrate control systems of a washing machine inaccordance with preferred embodiments of the present invention;

FIG. 4 illustrates a flow chart showing the steps of a method forcontrolling spinning of a washing machine of the present invention;

FIG. 5 illustrates a flow chart showing the steps of a method forcontrolling spinning of a washing machine in accordance with a preferredembodiment of the present invention; and

FIG. 6 illustrates a flow chart showing a method for controllingspinning of a washing machine in accordance with another preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Embodiments of the washing machine of the present invention will bedescribed with reference to FIGS. 2A˜6.

FIG. 2A illustrates a perspective view of a washing machine, having acontrol panel 100 on a front. The control panel 100 includes variousbuttons, a rotary key 200, and a display 300. The rotary keys 200 andbuttons are connected to a control unit 103. As the user rotates therotary key 200, rotation speeds of the motor and the drum are adjusted.

The buttons include a selection button 101, and a storage button 102.The selection button 101 is provided for selecting one of coursesoperative in various speeds depending on kinds of laundry, and thestorage button 102 is provided to store the adjusted speed in thecontrol unit. Moreover, a test mode button 110 is provided additionally,for selecting a test mode in which the rotation speed is set separatelyto avoid the resonance of the drum.

FIG. 2B illustrates a graph showing variation of rotation speed duringprogress of spinning of a washing machine.

Referring to FIG. 2B, the spinning step of the washing machine includesan eccentricity detecting step, additionally. That is, in the spinningstep, the eccentricity of the laundry and a foam quantity are detected.It is preferable that the detection of the eccentricity is performed ata rotation speed in the vicinity of 108 rpm at which the laundry startsto be in close contact with an inside surface of the drum.

In this instance, the eccentricity is detected by detecting variation ofthe rotation speed. The eccentricity is small when the rotation speed ofthe drum is uniform, and the eccentricity is great if the rotation speedof the drum varies sharply and periodically.

It is preferable that the eccentricity is detected, and corrected beforeperforming the spinning step. The spinning of the drum in a state theeccentricity of the laundry is great might give damage to the drum andthe rotation shaft.

In the meantime, if a resonance occurs between the drum and the rotationshaft, which spin, and the cabinet which supports them, the detection ofthe eccentricity is difficult. That is, when the rotation speed of thedrum is the same with the natural frequency of the frame, the resonanceoccurs. In this instance, since the vibration and noise produced fromthe drum increase sharply, and the rotation speed of the drum becomeserratic, accurate measurement of the eccentricity is not possible.

Therefore, it is required to know a rotation speed of the drum at whichthe resonance occurs in advance, for measuring the eccentricity in arange outside of the rotation speed at which the resonance occurs.

FIGS. 3A˜3C illustrate control systems of a washing machine inaccordance with preferred embodiments of the present invention.

Referring to FIG. 3A, the washing machine includes a control unit, amotor 104, a sensor 105, a selection button 101, a storage button 102, arotary key 200, a display 300, and a speaker 400.

The selection button 101 is connected to the control unit 103, forselecting an operation of desired course according to a kind of laundry.Therefore, if one of courses is selected with the selection button 101,the motor 104 rotates at a rotation speed set to meet a courserequirement. The rotation speed of the motor 104 is measured at thesensor 105, and provided to the control unit 103, and displayed on thedisplay 300. The rotary key 200 is provided for the user to change therotation speed.

If the resonance occurs at the drum, vibration or noise increasessharply. In this instance, for avoiding the resonance, the user turnsthe rotary key 200 to adjust the rotation speed, and presses the storagebutton 102, to store the adjusted rotation speed in the control unit103.

In the meantime, the washing machine further includes the speaker 400connected to the control unit 103, so that the speaker 400 sounds analarm when the resonance of the drum is detected, or the adjustedrotation speed is stored.

In the meantime, referring to FIG. 3B, the washing machine can detectthe resonance at the drum by means of a resonance detecting device 150,automatically.

The resonance detecting device 150 includes a spring and a groundingpart. If the spring vibrates more than a preset level, the spring comesinto contact with the grounding part, when a signal indicating that theresonance is occurred is generated.

That is, if the resonance occurs at the drum, an amplitude of thevibration becomes great suddenly, and the resonance detecting device 150provides the signal that the resonance occurs to the control unit 103 ina case a vibration value exceeds a preset value. In this instance, thecontrol unit 103 having received the signal adjusts the rotation speedof the drum, automatically. Of course, the adjustment of the rotationspeed may be made by the user manually by turning the rotary key.

In the meantime, the speaker 400 connected to the control unit 103sounds alarm when resonance of the drum is detected, or the adjustedrotation speed is stored. It is preferable that the adjusted rotationspeed is stored automatically by the control unit 103.

In the meantime, referring to FIG. 3C, the washing machine furtherincludes test mode buttons 110 connected to the control unit 103.

It is preferable that the step of adjusting the rotation speed foravoiding the resonance of the drum is made before a regular spinningoperation of the washing machine. Therefore, the step of adjusting therotation speed is performed after the user selects the test mode button110. The adjusted rotation speed is stored in the control unit beforethe test mode is finished.

Accordingly, when the regular spinning operation is performed againafter the test mode is finished, the drum rotates at the adjustedrotation speed.

A method for controlling spinning of the washing machine will bedescribed.

FIG. 4 illustrates a flow chart showing the steps of a method forcontrolling spinning of a washing machine of the present invention.

A method for controlling a washing machine of the present invention willbe described, with reference to FIG. 4.

At first, the drum is rotated at a first rotation speed set at thecontrol unit (S1). In order to detect the eccentricity of the laundry,it is preferable that the first rotation speed is in the vicinity of 108rpm. As described before, it is preferable that the detection of theeccentricity is made in a state no resonance occurs at the drum.

Therefore, occurrence of the resonance at the drum rotating at the firstrotation speed is detected (S2). If the resonance is detected at thedrum, the rotation speed of the drum is changed, automatically, ormanually (S3). It is preferable that an alarm sounds from the speaker ifthe resonance occurs at the drum for the user to know.

It is preferable that the rotation speed is increased or decreased, by apreset unit greater than 50 rpm. This is, since a resonance range of thedrum varies a certain level with a small variation of the eccentricityof the laundry, for changing the rotation speed of the drum greater thana variation range. That is, for securer avoidance of the resonanceoccurrence, the rotation speed is changed by predetermined magnitudeseach greater than a certain rpm.

In the meantime, even if the user can know the occurrence of resonanceat the drum from sudden increase of vibration and noise in the step (S2)of detecting resonance of the drum, it is preferable that the occurrenceof resonance is detected automatically by the resonance detectingdevice.

The resonance detecting device provides the signal that the resonance isoccurred to the control unit, automatically. It is preferable that therotation speed is changed by the control unit which received the signalfor avoiding the resonance, and the changed rotation speed is stored inthe control unit as a new first rotation speed. Accordingly, when thewashing machine is put into operation again after the washing machine isstopped, the drum is controlled to rotate at the changed rotation speed.

After change of the rotation speed, a step (S5) for measuringeccentricity of the laundry held in the drum is performed.

In a case the eccentricity is greater than a preset value, a step fordecreasing the rotation speed of the drum after increasing the rotationspeed of the drum is repeated. That is, by repeating the step of varyingthe rotation speed, the laundry is made to be spread evenly on an insidesurface of the drum, by which the eccentricity of the laundry iscorrected to an appropriate level.

Alternatively, for correcting the eccentricity to a desired level, thedrum may be rotated in regular/reverse directions alternately for aplurality of times. In cases the eccentricity is corrected to a valuebelow the preset level, or the detected eccentricity is below the presetlevel, the rotation speed of the drum is increased, to progress thespinning.

Opposite to this, in a case no resonance occurs at the drum rotating atthe first rotating speed, instead of changing the rotation speed of thedrum, a step (S6) for measuring eccentricity of the laundry held in thedrum is progressed, directly.

In this instance, as described before, if the measured eccentricity isgreater than the preset value, the step of decreasing the rotation speedof the drum after increasing the rotation speed of the drum is repeated,or the drum is rotated in regular/reverse directions alternately for aplurality of times.

In cases the eccentricity is corrected to a value below the presetlevel, or the detected eccentricity is below the preset level, therotation speed of the drum is increased, to progress the spinning.

It is preferable that the step (SA) for changing the rotation speed foravoiding the resonance, and the detection (S5, and S6) of eccentricityof the laundry are performed in a state the test mode is selected.

As described before, after finish of detection and correction of theeccentricity of the laundry held in the drum, the spinning step isprogressed.

In the meantime, FIG. 5 illustrates a flow chart showing the steps of amethod for controlling spinning of a washing machine in accordance witha preferred embodiment of the present invention.

Referring to FIG. 5, the drum is rotated at a constant speed of a presetsecond rotation speed for extraction of water from the laundry (S7).

The second rotation speeds corresponding to kinds of laundry, such aslingerie, blue jeans, general clothes, and blanket, are set at thecontrol unit. Therefore, once a desired course is selected by the userby pressing the selection button according to kind of the laundryinitially, the drum is rotated at the second rotation speed of theselected course. It is preferable that the second rotation speed ishigher than 600 rpm for smooth extraction of water from the laundry.

Referring to FIG. 2B, it is preferable that a step is further performed,for detecting a volume of foam inside of the drum while rotating thedrum at a constant speed of a third rotation speed (W12) before therotation speed is increased from the first rotation speed W1 to thesecond rotation speed W2.

Then, if resonance occurs at the drum rotating at the second rotationspeed W2 is detected (S8), if the resonance is detected, the rotationspeed of the drum is changed (S9). The changed rotation speed is storedin the control unit (S10).

It is preferable that the change of the rotation speed is made bypredetermined magnitudes each greater than 50 rpm. This is for changingthe rotation speed of the drum greater than a change range of aresonance range of the drum caused by a minute change of theeccentricity of the laundry.

In the meantime, it is preferable that the rotation speed change foravoidance of the resonance is made in a state the test mode is selected.After finish of the rotation speed change, the test mode is finishedautomatically, and, then, the spinning step proceeds for a preset timeperiod by spinning the drum.

For an example, if the initially set second rotation speed is 700 rpm ina selected course, and the resonance occurs at the rotation speed, therotation speed is changed by turning the rotary key, or automatically bythe control unit. Then, the rotation speed is changed to 650 rpm, andstored in the control unit. Thereafter, when the test mode is finished,and the washing machine is put into operation again, the drum performsthe spinning at the 650 rpm which is newly stored second rotation speed.

In this instance, the rotation speed of the drum is displayed on thedisplay 300, wherein, even if the spinning is progressed at 650 rpmactually, it is preferable that the rotation speed is displayed on thedisplay as 700 rpm as set initially. That is, at a time the washingmachine is put into operation again after the washing machine isstopped, not the changed rotation speed, but the second rotation speedset initially is displayed on the display 300. This is for preventingthe user from confusing on the rotation speed.

In the meantime, the display may display the changed rotation speed andthe initially set second rotation speed alternately at regular timeintervals.

FIG. 6 illustrates a flow chart showing a method for controllingspinning of a washing machine in accordance with another preferredembodiment of the present invention.

A method for controlling a washing machine will be described withreference to FIG. 6, in which a rotation speed of a drum is controlledfor extraction of water from laundry.

At first, the drum is rotated at the second rotation speed set at thecontrol unit (S12). In the spinning step, it is preferable that thesecond rotation speed is set different from each other according tokinds of laundry. For this, the spinning step further includes a stepfor selecting one of courses corresponding to a kind of the laundry, anda step for rotating the drum at a second rotation speed relevant to theselected course.

That is, second rotation speeds are set at the control unit for variouskinds of laundry, such as lingerie, blue jeans, general clothes, andblanket, respectively. Therefore, once the user selects a desired courseby pressing the selection button according to kind of the laundry, thedrum is rotated at the second rotation speed of the selected course.

The rotation speed is increased in succession by predetermined magnitudeof rpm from the second rotation speed (S15, and S17), and whether theresonance occurs at the drum or not is detected at every rotation speedsection (S14, S16, and S18). It is preferable that the predeterminedmagnitude of rpm is 50 rpm or 1000 rpm.

That is, if the resonance is detected at any one section of the rotationspeed, the rotation speed of the drum is changed (S20), and if noresonance is detected, after the rotation speed is increased bypredetermined magnitudes of rpm, whether the resonance occurs or not isdetected, again.

For an example, a case is assumed in which the drum rotates at 500 rpmwhich is initially set second rotation speed. If no resonance occurs,the rotation speed is increased to 600 rpm. If the resonance occurs atthe increased rotation speed, the rotation speed is decreased to 650 rpmor increased to 700 rpm.

In a case resonance is detected at the drum, the rotation speed of thedrum is increased or decreased, preferably by predetermined magnitudeseach greater than 50 rpm. According to this, occurrence of the resonanceat the changed rotation speed can be prevented, securely.

Thus, the rotation speed is adjusted for preventing occurrence of theresonance at the drum, and the adjusted rotation speed is stored in thecontrol unit. If the resonance of the drum is detected, an alarm soundsform the speaker, by which the user can know occurrence of theresonance, easily.

In the meantime, the control unit has a maximum rotation speed settherein, and, in a case no resonance occurs until the drum rotates up tothe set maximum rotation speed, the maximum speed is stored in thecontrol unit.

It is preferable that the detection of resonance at the drum S14, S16,and S18, the change of the rotation speed S20, and the storage of thechanged rotation speed S21 are performed in a state the test mode isselected S21.

Since the changed rotation speed is stored as a newly set secondrotation speed in the control unit, when the washing machine is put intooperation again after the test mode is finished, the drum is rotated atthe changed rotation speed directly, instead of increasing the rotationspeed gradually.

In the meantime, an alarm sounds from the speaker when the changedrotation speed is stored in the control unit, and the storage of thechange rotation speed is performed automatically by the control unit inresponse to the signal from the resonance detecting device. Moreover, itis preferable that the occurrence of the resonance at the drum isdetected by the resonance detecting device, automatically.

It is preferable that the washing machine is provided with a resetbutton for returning the rotation speed to the initialed set secondrotation speed, for making the next operation by the user in performingthe test mode easy.

As has been described, the washing machine and the method forcontrolling the same have the following advantages.

First, the method for controlling a washing machine of the presentinvention permits more accurate measurement of an eccentricity bydetecting resonance and adjusting the rotation speed in measuringeccentricity of the laundry held in the drum.

Second, the detection of resonance at a rotation speed of the drum andadjustment of the rotation speed to avoid the resonance in the spinningstep permits to enhance reliability of the product.

The foregoing method for controlling spinning in a washing machine isapplicable not only to the drum type washing machine, but also othergeneral washing machines, such as a pulsator type washing machine.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-18. (canceled)
 19. A method for controlling a washing machine having adrum of which rotation speed is adjustable for extracting water fromlaundry, comprising: a first step for rotating the drum at a secondrotation speed set at a control unit; a second step for increasing therotation speed from the second rotation speed by predeterminedmagnitudes of rpm in succession, and whether resonance occurs or not atevery rotation speed section is detected; a third step for changing therotation speed of the drum when resonance of the drum is detected; and afourth step for storing the changed rotation speed in the control unit.20. The method as claimed in claim 19, wherein the first step includesthe steps of; selecting one of course relevant to a kind of laundry, androtating the drum at the second rotation speed for the selected course.21. The method as claimed in claim 19, wherein the rotation speed of thedrum increases in the third step.
 22. The method as claimed in claim 19,wherein the rotation speed of the drum decreases in the third step. 23.The method as claimed in claim 19, wherein the rotation speed of thedrum changes by predetermined magnitudes each greater than 50 rpm in thethird step.
 24. The method as claimed in claim 19, wherein the steps areperformed in a state a test mode is selected.
 25. The method as claimedin claim 24, wherein the drum is rotated at the changed rotation speedwhen the washing machine is put into operation again after the test modeis finished.
 26. The method as claimed in claim 25, wherein, not thechanged rotation speed, but the second rotation speed is displayed on adisplay, when the washing machine is put into operation again after thewashing machine is stopped.
 27. The method as claimed in claim 19,wherein the fourth step includes the step of sounding an alarm from aspeaker when the changed rotation speed is stored.
 28. The method asclaimed in claim 19, wherein the third step is performed automaticallyby the control unit having the signal received from a resonancedetecting device.
 29. The method as claimed in claim 19, wherein thesecond step includes the step of automatic detection of resonanceoccurrence at the drum by the resonance detecting device.
 30. The methodas claimed in claim 19, wherein the second step further includes thestep of storing a preset maximum rotation speed in the control unit in acase no resonance occurs until the drum rotates up to the preset maximumspeed.
 31. The method as claimed in claim 19, wherein the second stepfurther includes the step of sounding an alarm from a speaker if theresonance of the drum is detected. 32-38. (canceled)